Berkeley’s Smart Dust project, led by Professors
Pister and Kahn, explores the limits on size and power consumption in
autonomous sensor nodes. Size reduction is paramount, to make the nodes as
inexpensive and easy-to-deploy as possible. The research team is confident that
they can incorporate the requisite sensing, communication, and computing
hardware, along with a power supply, in a volume no more than a few cubic
millimeters, while still achieving impressive performance in terms of sensor
functionality and communications capability. These millimeter-scale nodes are
called “Smart Dust.” It is certainly within the realm of possibility that
future prototypes of Smart Dust could be small enough to remain suspended in
air, buoyed by air currents, sensing and communicating for hours or days on
end.

Smart Dust Technology

Integrated into a single package are:-

1.
MEMS sensors

2.
MEMS beam steering mirror for active optical transmission

3. MEMS corner cube retroreflector for passive
optical transmission

4.An
optical receiver

5.
Signal processing and control circuitory

6. A
power source based on thick film batteries and solar cells

This remarkable package has the ability to sense
and communicate and is self powered. A major challenge is to incorporate all
these functions while maintaining very low power consumption.

Operation Of The Mote

The Smart Dust mote is run by a microcontroller
that not only determines the tasks performed by the mote, but controls power to
the various components of the system to conserve energy. Periodically the
microcontroller gets a reading from one of the sensors, which measure one of a
number of physical or chemical stimuli such as temperature, ambient light,
vibration, acceleration, or air pressure, processes the data, and stores it in
memory. It also occasionally turns on the optical receiver to see if anyone is
trying to communicate with it. This communication may include new programs or
messages from other motes. In response to a message or upon its own initiative
the microcontroller will use the corner cube retro reflector or laser to transmit
sensor data or a message to a base station or another mote.

The primary constraint in the design of the Smart
Dust motes is volume, which in turn puts a severe constraint on energy since we
do not have much room for batteries or large solar cells. Thus, the motes must
operate efficiently and conserve energy whenever possible. Most of the time,
the majority of the mote is powered off with only a clock and a few timers
running. When a timer expires, it powers up a part of the mote to carry out a
job, then powers off. A few of the timers control the sensors that measure one
of a number of physical or chemical stimuli such as temperature, ambient light,
vibration, acceleration, or air pressure. When one of these timers expires, it
powers up the corresponding sensor, takes a sample, and converts it to a
digital word. If the data is interesting, it may either be stored directly in
the SRAM or the microcontroller is powered up to perform more complex
operations with it. When this task is complete, everything is again powered
down and the timer begins counting again.

Communicating From A Grain Of Sand

Smart Dust’s full potential can only be attained
when the sensor nodes communicate with one another or with a central base
station. Wireless communication facilitates simultaneous data collection from
thousands of sensors. There are several options for communicating to and from a
cubic-millimeter computer.

Radio-frequency and optical communications each
have their strengths and weaknesses. Radio-frequency communication is well
under-stood, but currently requires minimum power levels in the multiple
milliwatt range due to analog mixers, filters, and oscillators. If whisker-thin
antennas of centimeter length can be accepted as a part of a dust mote, then
reasonably efficient antennas can be made for radio-frequency communication.
While the smallest complete radios are still on the order of a few hundred
cubic millimeters, there is active work in the industry to produce
cubic-millimeter radios.

Moreover RF techniques cannot be used because of
the following disadvantages: -

1. Dust motes offer very limited space for
antennas, thereby demanding extremely short wavelength (high frequency
transmission). Communication in this regime is not currently compatible with
low power operation of the smart dust.

2. Furthermore radio transceivers are relatively
complex circuits making it difficult to reduce their power consumption to
required microwatt levels.

3. They require modulation, band pass filtering
and demodulation circuitry.

Corner Cube Retroreflector

These MEMS structure makes it possible for dust
motes to use passive optical transmission techniques ie, to transmit modulated
optical signals without supplying any optical power.It comprises of three mutually perpendicular
mirrors of gold-coated polysilicon. The CCR has the property that any incident
ray of light is reflected back to the source (provided that it is incident
within a certain range of angles centered about the cube’s body diagonal).If
one of the mirrors is misaligned , this retro reflection property is spoiled.
The micro fabricated CCR contains an electrostatic actuator that can deflect
one of the mirrors at kilohertz rate. It has been demonstrated that a CCR
illuminated by an external light source can transmit back a modulated signal at
kilobits per second. Since the dust mote itself does not emit light , passive
transmitter consumes little power. Using a microfabricated CCR, data
transmission at a bit rate upto 1 kilobit per second and upto a range of 150 mts
,using a 5 milliwattt illuminating laser is possible.

It should be emphasized that CCR based passive
optical links require an uninterrupted line of sight. The CCR based transmitter
is highly directional. A CCR can transmit to the BTS only when the CCR body
diagonal happens to point directly towards the BTS, within a few tens of
degrees. A passive transmitter can be made more omnidirectional by employing
several CCRs, oriented in different directions, at the expense of increased
dust mote size.

Core Functionality Specification

Choose the case of military base monitoring
wherein on the order of a thousand Smart Dust motes are deployed outside a base
by a micro air vehicle to monitor vehicle movement. The motes can be used to
determine when vehicles were moving, what type of vehicle it was, and possibly
how fast it was travelling. The motes may contain sensors for vibration, sound,
light, IR, temperature, and magnetization. CCRs will be used for transmission,
so communication will only be between a base station and the motes, not between
motes. A typical operation for this scenario would be to acquire data, store it
for a day or two, then upload the data after being interrogated with a laser.
However, to really see what functionality the architecture needed to provide
and how much reconfigurability would be necessary, an exhaustive list of the
potential activities in this scenario was made. The operations that the mote
must perform can be broken down into two categories: those that provoke an
immediate action and those that reconfigure the mote to affect future behavior.

Summary

Smart dust is made up of thousands of
sand-grain-sized sensors that can measure ambient light and temperature. The
sensors -- each one is called a "mote" -- have wireless communications
devices attached to them, and if you put a bunch of them near each other,
they'll network themselves automatically.

Today,
the interaction of human individuals with electronic devices demands specific
user skills. In future, improved user interfaces can largely alleviate this
problem and push the exploitation of microelectronics considerably. In this context
the concept of smart clothes promises greater user-friendliness, user
empowerment, and more efficient services support. Wearable electronics responds
to the acting individual in a more or less invisible way. It serves individual
needs and thus makes life much easier. We believe that today, the cost level of
important microelectronic functions is sufficiently low and enabling key
technologies are mature enough to exploit this vision to the benefit of
society. In the following, we present various technology components to enable
the integration of electronics into textiles.

Advances
in textile technology, computer engineering, and materials science are
promoting a new breed of functional fabrics. Fashion designers are adding
wires, circuits, and optical fibers to traditional textiles, creating garments
that glow in the dark or keep the wearer warm. Meanwhile, electronics engineers
are sewing conductive threads and sensors into body suits that map users'
whereabouts and respond to environmental stimuli. Researchers agree that the
development of genuinely interactive electronic textiles is technically
possible, and that challenges in scaling up the handmade garments will
eventually be overcome. Now they must determine how best to use the technology.

Electronic
textiles (e-textiles) are fabrics that have electronics and interconnections
woven into them. Components and interconnections are a part of the fabric and
thus are much less visible and, more importantly, not susceptible to becoming
tangled together or snagged by the surroundings. Consequently, e-textiles can
be worn in everyday situations where currently available wearable computers
would hinder the user. E-textiles also have greater flexibility in adapting to
changes in the computational and sensing requirements of an application. The
number and location of sensor and processing elements can be dynamically
tailored to the current needs of the user and application, rather than being
fixed at design time. As the number of pocket electronic products (mobile
phone, palm-top computer, personal hi-fi, etc.) is increasing, it makes sense
to focus on wearable electronics, and start integrating today's products into
our clothes. The merging of advanced electronics and special textiles has
already begun. Wearable computers can now merge seamlessly into ordinary
clothing. Using various conductive textiles, data and power distribution as
well as sensing circuitry can be incorporated directly into wash-and-wear
clothing.

Wireless World

Whatever
the technical obstacles, researchers involved in the development of interactive
electronic clothing appear universally confident that context-aware coats and
sensory shirts are only a matter of time. Susan Zevin, acting director of the
Information Technology Laboratory at the US National Institute of Standards and
Technology (NIST), would like to see finished garments fitted with some form of
data encryption system before they reach consumers. After all, wearing a jacket
that is monitoring your every movement, recording details about your personal
well-being, or pinpointing your exact location at a moment in time, adds a
whole new dimension to issues of wireless security and personal privacy.

"The
challenge, I think, for industry is to build in the security and privacy before
the technology is deployed, so the user doesn't have to worry about having his
or her T-shirt attacked by a hacker, for example," says Zevin.
"People don't want to have to upload and download intrusion detection
systems themselves. Pervasive computing should also mean pervasive computer
security, and it should also mean pervasive standards and protocols for
privacy." She notes that the level of security required for electronic
textile garments will vary according to their applications.

Project Examples

Wearable Antennas

In
this program for the US Army, Foster-Miller integrated data and communications
antennas into a soldier uniform, maintaining full antenna performance, together
with the same ergonomic functionality and weight of an existing uniform. We
determined that a loop-type antenna would be the best choice for clothing
integration without interfering in or losing function during operations, and
then chose suitable body placement for antennas. With Foster-Miller's extensive
experience in electro-textile fabrication, we built embedded antenna prototypes
and evaluated loop antenna designs. The program established feasibility of the
concept and revealed specific loop antenna design tradeoffs necessary for field
implementation.

This
program provided one of the key foundations for Foster-Miller's participation
in the Objective Force Warrior program, aimed at developing soldier ensemble of
the future, which will monitor individual health, transmit and receive
mission-critical information, protect against numerous weapons, all while being
robust and comfortable.

Limitations and Issues of the "Smart
Shirt"

Some
of the wireless technology needed to support the monitoring capabilities of the
"Smart Shirt" is not completely reliable. The "Smart Shirt"
system uses Bluetooth and WLAN. Both of these technologies are in their
formative stages and it will take some time before they become dependable and
widespread.

Additionally,
the technology seems to hold the greatest promise for medical monitoring.
However, the "Smart Shirt" at this stage of development only detects
and alerts medical professionals of irregularities in patients' vital
statistics or emergency situations. It does not yet respond to dangerous health
conditions. Therefore, it will not be helpful to patients if they do face
complications after surgery and they are far away from medical care, since the
technology cannot yet fix or address these problems independently, without the
presence of a physician. Future research in this area of responsiveness is
ongoing.

Fabric Computing Devices

Designing
with unusual materials can create new user attitudes towards computing devices.
Fabric has many physical properties that make it an unexpected physical,
interface for technology. It feels soft to the touch, and is made to be worn
against the body in the most intimate of ways. Materially, it is both strong
and flexible, allowing it to create malleable and durable sensing devices.
Constructing computers and computational devices from fabric also suggests new
forms for existing computer peripherals, like keyboards, and new types of
computing devices, like jackets and hats.

Monday, November 28

3D
printing is a form of additive manufacturing technology where a three
dimensional object is created by laying down successive layers of material. It
is also known as rapid prototyping, is a mechanized method whereby 3D objects
are quickly made on a reasonably sized machine connected to a computer
containing blueprints for the object.

Stereo Lithography 3D Printers

Stereo
lithographic 3D printers (known as SLAs or stereo lithography apparatus)
position a perforated platform just below the surface of a vat of liquid photo
curable polymer. A UV laser beam then traces the first slice of an object on
the surface of this liquid, causing a very thin layer of photopolymer to
harden. The perforated platform is then lowered very slightly and another slice
is traced out and hardened by the laser. Another slice is then created, and
then another, until a complete object has been printed and can be removed from
the vat of photopolymer, drained of excess liquid, and cured.

Inkjet 3D Printing

It
creates the model one layer at a time by spreading a layer of powder and inkjet
printing binder in the cross-section of the part. It is the most widely used
3-D Printing technology these days and the reasons beyond that are stated
below.

3) No toxic chemicals like those used in
stereo lithography are required.

4) Minimal post printing finish work is
needed; one needs only to use the printer itself to blow off surrounding powder
after the printing process.

5)
Allows overhangs and excess powder can be easily removed with an air blower.

System Overview

Our
3D printing process is automatic, and thus easy for any user. Still, a lot is
taking place under the hood. This section provides an overview of the ZPrinter
system and the steps involved in printing a 3D physical model. We will refer to
the 3D printer diagram in Figure 2 as we detail the 3D printing process

1)
Automatic air filter: ensures that all powder stays within the confines of the
machine, emitting only clean air into the office or workroom environment.

Our
vision of making on-demand prototyping accessible to everyone requires that
printing a model be almost as easy as printing a document. We envisioned that
every designer, engineer, intern or student should be able to ZPrint a
prototype. And like a document printer, a 3D printer should be perfectly
compatible with a professional office environment.

To
achieve these goals, the ZPrinter automates operation at nearly every step.
This includes setup, powder loading, self-monitoring of materials and print
status, printing, and removal and recycling of loose powder. The ZPrinter is
quiet, produces zero liquid waste and employs negative pressure in a
closed-loop system to contain airborne particles. Powder and binder cartridges
ensure clean loading of build materials. Plus, an integrated fine-powder
removal chamber reduces the footprint of the system. All of these advances mean
that no special training is required, and the “hands on” time for operating the
3D printer is just a few minutes.

You
control the ZPrinter from either the desktop or the printer. ZPrint software
lets you monitor powder, binder, and ink levels from your desktop, and remotely
read the machine’s LCD display. The on-board printer display and intuitive
interface enables you to perform most operations at the machine. Plus, the ZPrinter
runs unattended during the printing process, requiring user interaction only
for setup and part removal.